How to Turn Your Bathtub Into a Giant iPad

Close your eyes and imagine how it would feel to go for a swim inside your iPad’s touchscreen. It could be a little like the surreal, interactive “AquaTop display” experience, created by researchers at the University of Tokyo Electro Communications Laboratory. The prototype model is just a tank of water, but the plan is for the AquaTop to turn your everyday bathtub into an immersive touchscreen, allowing the bather to watch movies, look at photos and play games.

Unlike your typical touchscreen, the user doesn’t just have control from above the screen’s surface. It’s designed so that you can feel like a part of the screen. Because the touch-sensing area extends a few centimeters below the water's surface, the system responds to a variety of commands including scooping water, waving your arm across the water, “pulling” images underwater to delete them and “clicking” with one, two or three fingers from both above and below the surface.

The way it works is fairly simple. Add bath salts--magnesium sulfate, not the mind-altering drugs--to the water, giving it a pale murky color so that images can be cast onto the water’s surface by a projector mounted above and opposite the bathtub. A Microsoft Kinect serves as a depth camera so the system can respond to commands from both the water’s surface and within the water. An array of 80-millimeter speakers produce 50Hz waves that deliver haptic feedback to the user. In a demonstration, a 250-millimeter speaker, to which a grid of red LEDs was attached, created a light-up mini-fountain within the tub and was used to indicate explosions in a video game played on the water's surface. The elements are all conducted by a master control computer, which you should be careful not to splash.

AquaTop has both “desktop interactions,” which allow the bather to view movies and look at pictures, and “game interactions.” The makers have created a “shooting jellyfish” game, where fingers and hands control “magic circles” and “fireballs” used to battle enemy jellyfish or a floating plastic rubber duck capable of fighting back. There’s also a two-player mode, for when the bather has company.

The researchers hope to soon introduce a version of the AquaTop suitable for at home use. They also envision a version for theme parks and swimming pools.

The researchers cite “hands becoming wet” as the only disadvantage of the AquaTop display. But I’d also like to add the dangerous levels of laziness that could come from turning your bathtub into a big screen TV. That and the risk of knocking the adjoined computer, Kinect, or projector into the tub. No one wants to be that guy.

Photo: The University of Electro-Communications Koike Laboratory

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